S6 won't turn on even with hard reset

I took my phone out of my pocket this afternoon only to find that the screen was blank and the only thing that seems to be working is the blue led notification light that keeps changing to different shades of blue. I had a look on websites and they told me to hard reset (all four buttons / volume down + power / three buttons etc) - I've tried every button combination and it isn't working. It had around 50% battery when it died and I'm charging it right now. I can't find the warranty and I would really rather try and sort this myself because I don't have the money to fix it. Can anyone help?